The use of synthetic amphoteric polymers in photographic silver halide emulsions is known. Hollister et al. U.S. Pat. No. 3,749,577 discloses a photographic silver halide emulsion containing polymers prepared by direct polymerization of monomers having a carboxyl functionality, e.g., acrylic acid, and monomers having a quaternary ammonium functionality. Hollister et al. U.S. Pat. No. 3,813,251 discloses such a use for similar polymers having a tertiary ammonium functionality.
Smith et al U.S. Pat. No. 3,692,753 discloses a silver halide emulsion containing amphoteric polymers of, e.g., N,N-dimethyl- and N,N-diethylaminoethyl methacrylate, acrylic acid, and acrylamides or acrylates having thioalkyl groups in the alkyl chain.
U.K. Patent Specification No. 889,760 discloses light-sensitive emulsions to which are added synthetic amphoteric polymers prepared by hydrolysis of polymers containing groups capable of producing acidic and basic groups on hydrolysis.
Assignee's Foss patent application Ser. No. 377,373, filed May 12, 1982, discloses specified synthetic amphoteric polymers which can be added during the precipitation of silver halide emulsions and serve as a partial or complete replacement for gelatin.
In the above United States patents the presence of a synthetic amphoteric polymer acts as a peptizing agent in the precipitation and ripening step during the preparation of a photographic silver halide emulsion. In the United Kingdom patent the additon of amphoteric polymers during silver halide emulsion preparation is said to improve the emulsion, e.g., high silver concentration and the silver halide from such emulsions can be rapidly washed and finally redispersed. Assignees' Foss application Ser. No. 377,373, filed May 12, 1983 discloses the preparation of specified synthetic amphoteric polymers which can serve as a partial or complete replacement for the gelatin binder of a silver halide emulsion.
Although the aforementioned patents and application seek to improve either film variability due to the physical and chemical variabilities found in gelatin or one or more of various physical properties such as film toughness, they do not consider the particular problem of image sharpness in wash-off films. The preparation of wash-off films is known from disclosures such as U.S. Pat. Nos. 3,353,958; 3,364,024; 3,440,049; 3,453,111; 3,615,529; 3,856,524; 4,076,531; 4,233,392; 4,427,757 and 4,456,676, the disclosures of which are incorporated by reference. In common, these reference disclose the use of unhardened gelatin as the binder for wash-off films in which tanning development takes place to harden the gelatin in proximity with developing silver. Unhardened gelatin is then washed away to produce the wash-off image. Apparently due to the gelling characteristics of the gelatin binder as well as diffusion of oxidized developer responsible for the hardening action outside of the areas of developing silver, the sidewalls of the resulting relief image is often jagged which results in loss of image resolution.
It is desirable to provide a wash-off film for tanning development having one or more unhardened gelatin layers, including an unhardened silver halide emulsion layer, wherein a portion of the gelatin is replaced by a water soluble synthetic amphoteric polymer wherein upon imagewise exposure and development a sharper wash-off image is obtained.